I just got online but wished I gotcha before you started your voyage! But If you have not left yet or even if you stop for a drink n food by a convenience store......grab about 3 of the 10 lbs bags and 3 gallons of water.
With the age of your Prowler, be surprised if if had an electronic sensor board to monitor the amount of waste in the Black Tank. But any mindful Human Being would not sell the Rig to you with it full (right?) so I will assume she is empty.
No make sure your your black waste valve is closed (should be closed obviously as you are traveling, gray tanks too!)
Slam the ice to the ground pavement to loosen each bag up real good! Now take the 1st bag and slowly empty into the toilet, then followed by a gallon of water. Repeat the process for all the bags of ice n water.
So now.....while your driving on the highway making turns, bumps, etc. the small ice blocks will act as rocks and bang up against the steel walls and hitting the solid waste n TP along the way!!! This action will remove all this sediment etc. from the electronic sensors or probes. And even if you don't have the sensors, the ice will still "knock the hard around" and all will loosen in the ice melting with water mixture!!! Solution? Rid the tank of all solid waste so when you get home (let sit at least 24 hours as I don't know how long your drive is) then open your black waste valve and watch the now mostly brown soup poop exit into your septic line.
Tip: After the brown poop stops on its own (and you should invest in a clear fitting so you can see when all the waste has exited), now put a very heavy brick etc. on the toilet foot pedal to force and leave it open!!! Or I use my toilet brush to keep it open, as long as you get n keep the water running down to the toilet.
Now go outside and wait till what you see!!! You thought the black waste tank was empty and free of all poop right? Nope! You will see the brown glump out now and let the water run for as long as it takes till you see clear water coming out!
(note: there are other waste clean out options, but the one above is basic and does not cost a dime) except for the ice n water....LOL